Reaction products of n-heterocyclic ammonium thiocyanates and aldehydes



Patented Jan. 26, 1954 CROSS REFERENCE REACTION CLIC AMIMONIUM ALDEHYDESPRODUCTS OF N-HETEBOCY- THIOCYANATES AND William H. Hill, Pittsburgh,Pa., assignor to Koppers Company, Inc., Pittsburgh, Pa, a. corporationof Delaware No Drawing. Original application November 26,

1946, Serial No. 712,253. Divided and this al plication March 8, 1951,Serial No. 218,089

6 Claims. (Cl. 260-2943) This invention relates to compositions ofmatter and is particularly directed to products of l gsr ndensation ofan aldehyde and a preformed salt of a thiocyanic acid and certainnitrogen 'cbfii'pounds.

This application is a division of my copending application Serial No.712,253, filed November 26, 1946, now U. S. Patent No. 2,606,155,granted Aug. 5, 1952.

The new products of the invention are useful as inhibitors incleaningmetals, as more particularlyset forth in U. S. Patent No.2,425,320, granted August12, 1947, on my copending application, SerialNo. 463,133, filed October 23,

1942, of which the present application is in part a continuation; asrubber accelerators; as pest control agents; and as synthetic resins andplasties.

The nitrogen compounds from which the salts of thiocyanic acids areprepared are basic heterocyclic amino compounds. They contain one ormore amino or imino groups, or tertiary or quarternary nitrogen atoms,or combinations thereof in which the amino nitrogen atom is an elementof a heterocycle. It is to be understood in the present instance thatthe term heterocyclic amino compound as herein employed, applies tocompounds containing secondary, tertiary and quaternary amine structuresin their configuration and wherein two or three atoms of ammoniahydrogen have been replaced by other linkages.

The stronger the basic characteristics of the amino compound used as astarting material the better the compound is for purposes of the presentinvention. It is preferred that the amino compound be basic enough toform with thiocyanic acid true thiocyanates of sufficient stability toavoid continuous splitting off of free thiocyanic acid in too greatproportions during condensation. The bases employed should preferablyhave a basicity greater than that expressed by the dissociation constant10-14.

The presence of water solubilizing groups, such as N112, NH, on andothers, in the amino compound or in the inhibitor product b'rlififponthe inhibitor increased solubility in the acid baths in which it isused.

In particular the invention is directed to condensation products of analdehyde and preformed heterocyclic ammonium salt of a thiocyanic acid.

The following are some of the amino compounds which have been found tobe useful in providing the acid inhibitors of the present invention:

Pyridine, alpha picoline, 2,6-lutidine, quinoline, quinaldine, nicotine,piperidine, morpholine, phenylmorpholine, and phenylmethyl pyrazolone.

The above amino compounds, either singly or mixtures of two or morethereof, or in admixture with other basic amino compounds are readilyconverted to salts of a thiocyanic acid (e. g. thiocyanic acid, orperthiocyanic acid) by reaction with the thiocyanic acid or by thedouble decomposition of another aminesalt and a metal or ammonium saltof the thiocyanic acid.

For thealdehyde component of the new compounds there may be used forexample formaldehyde, acetaldehyde, butyraldehyde, crotonaldehyde,acrolein, benzaldehyde, salicylaldehyde, cinnamic aldehyde, furfural,glyoxal, and others and mixtures thereof. Formaldehyde is in general tobe preferred on account of its availability, cheapness, andeffectiveness.

As to the relative proportion of amino compound and-aldehyde to be used,no general rule can be laid down. The ratio depends on the number ofactive groups in the amino compound molecule, such as N'Ha andthiocyanate groups. One mol of aldehyde is usually employed for eachreactive group, and therefore in most cases two mols of aldehyde aresuflicient for a particular thiocyanate. In using the products forpickling inhibitors, however, an excess of, for example, formaldehydedoes no harm, since it is in itself a. pickling inhibitor of somelimited value and may therefore be left with the reaction product inmany cases. A deficiency of aldehyde also is of no grave consequence ifthe products are used as inhibitors, since practically all amines andthiocyanates in a sense have some inhibiting value of their own. Wheredesired, an excess of aldehyde may be removed by means known to the art,such as evaporation in vacuo or otherwise.

When using the products as pickling inhibitors, it is often advantageousto add wetting agents to the pickling baths or to incorporate suchagents with the inhibitors themselves. Such commercial wetting agents asa naphthalene sulphonic acid type of wetting agent, known as Aerosol OS,render good service. They should be employed in quantities of about ofthe acid weight of the bath. The addition of wetting agents facilitatesthe removal of carbon smut from pickled steel or other metal goods. Atthe same time, though only very small amounts of the inhibitors areneeded in a pickling bath in order to inhibit effectively the solventaction of the acid in the bath on the metal as seen in the followingexamples, the addition of the wetting agent increases the effectivenessof the inhibitors to such an extent that substantially smallerpercentages of the inhibitors give satisfactory results.

The following examples, in which the parts are by weight unlessotherwise specified, are illustrative.

Example 1 76 g. of alpha-picoline thiocyanate (0.5 mol) is mixed with 75cc. (1 mol) of 40% aqueous formalin solution. The resultant light yellowliquid is refluxed for two hours under a reflux condenser. Evaporationof the condensation product on a steam bath yields a gray-white brittlesolid.

Example 3 83 g. (0.5 mol) of 2,6-lutidine thiocyanate is mixed with 75cc. (1 mol) of 40% aqueous formalin solution. The thiocyanate dissolvescompletely at room temperature with absorption of heat. The resultingyellow liquid is gently refluxed for two hours and is then evaporated ona steam bath yielding a red granular solid.

Example 4 94 g. (0.5 mol) of quinoline thiocyanate is mixed with '75 cc.(1 mol) of 40% aqueous formalin solution. Most of the thiocyanate goesinto solution with absorption of heat and the rest dissolves when themixture is refluxed for three hours. The resultant red-brown liquid isevaporated on the steam bath, yielding a red- 7 brown solid.

Example 5 202 g. (1 mol) of quinaldine thiocyanate is mixed with 150 cc.(2 mols) of 40% aqueous formalin solution. The thiocyanate saltdissolves easily and the resultant solution is light red in color. It isrefluxed gently for five hours and is then evaporated to yield an almostblack solid.

Example 6 88.4 g. (0.4 mol) of nicotine thiocyanate is mixed with 75 cc.(1 mol) of 40% aqueous formalin solution. The dark brown liquid isrefluxed for two hours. Evaporation on a steam bath yields a dark,syrupy liquid.

Example 7 146 g. (1 mol) of morpholine thiocyanate is mixed with 150 cc.(2 mols) of 40% aqueous formalin solution. The salt dissolves to a largeextent and goes completely into solution during the subsequent heatingunder reflux r five hours. The condensation product is eva orated tonear dryness and then constitutes a dark brown, viscous, oily liquid.

Example 8 202 g. of the thiocyanic acid salts of quinoline still residuebases (mixed tar bases of average molecular weight 143), constituting aviscous, dark-brown liquid, is mixed with 150 cc. of 40% aqueousformalin solution. The two liquids mix easily. The mixture is refluxedfor two hours. The almost black, viscous reaction product is evaporatedto a black, viscous liquid.

While inthe foregoing examples the condensation products were evaporatedin order to eliminate ballast water and possibly excess formaldehyde,this is not necessary. The products at the end of the condensationperiod may be used as such as pickling inhibitors.

I claim:

1. A composition of matter consisting essentially of a reaction productof an aldehyde and a pre-formed hetero-N-ammonium thiocyanate.

2. A composition of matter consisting essentially of the composition ofclaim 1 in which the aldehyde is formaldehyde.

3. A composition of matter consisting essentially of a reaction productof an aldehyde and a preformed thiocyanate of a basic mono-aminocompound having its nitrogen atom comprised in a single heterocycle.

4. A composition of matter consisting essentially of the composition ofclaim 3 in which the aldehyde is formaldehyde.

5. A composition of matter consisting essentially of a reaction productof an aldehyde and a preformed pyridinium thiocyanate.

6. A composition of matter consisting essentially of the composition ofclaim 5 in which the aldehyde is formaldehyde.

WJLLIAM H. HILL.

References Cited in the file of this patent UNITED STATES PATENTS HillAug. 12, 1947

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A REACTION PRODUCTOF AN ALDEHYDE AND A PRE-FORMED HETERO-N-AMMONIUM THIOCYANATE.